1. Field of the Invention
The present invention relates to an image forming apparatus, such as a printer, a facsimile machine, and a copier.
2. Description of the Related Art
In image forming apparatuses, residual substance, such as toner or paper dust, that remains on a photosensitive element after image transfer is scraped by a cleaning unit. The cleaning unit includes a cleaning blade with a sharp edge, and the sharp edge of the cleaning blade is pressed against the photosensitive element thereby scraping off the residual substance. With the continued use of the cleaning blade, foreign substances, such as toner or paper dust, are gradually stuck to the edge of the cleaning blade. The foreign substances stuck to the cleaning blade may be caught between the cleaning blade and a surface of the photosensitive element creating various problems. These problems include scattering of toner, generation of image defects such as streak lines in black or white on the image, and causing damage to the photosensitive element.
Japanese Patent Application Laid-open No. 2007-199169, Japanese Patent Application Laid-open No. 2004-264553, and Japanese Patent Application Laid-open No. 2007-164018 disclose techniques to remove foreign substances stuck to the edge portion of a cleaning blade. These conventional techniques teach providing a drive unit capable of driving a photosensitive element to rotate in any of a forward direction and a reverse direction. While the image forming apparatus is not performing image formation, the drive unit drives the photosensitive element to rotate in the reverse direction, i.e., in a direction opposite to a rotating direction when the image forming apparatus performs image formation (i.e., in the forward direction, in this case). When the photosensitive element rotates in the reverse direction it carries the foreign substance stuck to the edge of the cleaning blade.
Furthermore, there has been developed a process unit including an electronic-information storage unit such as an ID chip. The process unit as an image forming unit is removably mounted in an image forming apparatus. Operational information of the process unit and the like are stored in the electronic-information storage unit.
Moreover, there has been developed an image forming apparatus that an openable upper cover is provided on a top end portion of an enclosure of the image forming apparatus so that a process unit can be easily replaced with new one.
How the new process unit is mounted in the image forming apparatus is explained below with reference to FIGS. 10 to 13. FIG. 10 is a side perspective view of an example of a process unit 1Y for yellow. A process unit 1K for black, a process unit 1C for cyan, and a process unit 1M for magenta have substantially identical configuration as that of the process unit 1Y.
As shown in FIG. 10, an ID chip 35Y as an electronic-information storage unit and a plurality of communication electrodes 38Y are provided on a case 13Y of a side surface of the process unit 1Y. The communication electrodes 38Y are connected to respective input-output terminals (not shown) of the ID chip 35Y.
When attaching the process unit 1Y to a main body of the image forming apparatus (hereinafter, “the apparatus main body”), a user drops in the process unit 1Y downward from the upside of the image forming apparatus as shown in FIG. 11.
When the process unit 1Y is completely mounted in the apparatus main body, as shown in FIG. 12, a photosensitive-drum gear 2bY formed on an outer circumferential surface of a back-side flange, which is press-fitted into a back-side end of a photosensitive element 2Y, is engaged with a drive gear 99Y of the apparatus main body, and also the communication electrodes 38Y come in contact with contact electrodes 94Y provided on a back side plate 98 of the apparatus main body.
Furthermore, as shown in FIG. 13, the drive gear 99Y is arranged so that a top portion of the drive gear 99Y is positioned above a bottom portion of the photosensitive-element gear 2bY. Therefore, when the photosensitive element 2Y is driven to rotate in the forward direction, the process unit 1Y is subjected to a force in a vertically downward direction by the engagement between the drive gear 99Y and the photosensitive-element gear 2bY.
The ID chip 35Y stores therein information on a running distance of the photosensitive element 2Y, a remaining amount of toner, an amount of waste toner, and the like. A control unit (not shown) as a communicating unit in the apparatus main body writes information on the ID chip 35Y or reads out information from the ID chip 35Y via a contact between the contact electrodes 94Y and the communication electrodes 38Y while the photosensitive element 2Y is driven to rotate.
However, when the photosensitive element 2Y is driven to rotate in the reverse direction to remove a foreign substance stuck to a cleaning blade, as shown in FIG. 13, the process unit 1Y is subjected to a force in a vertically upward direction. As a result, the process unit 1Y may be uplifted. If the process unit 1Y is uplifted, a contact pressure between the communication electrodes 38Y and the contact electrodes 94Y is reduced, and thus a contact failure may be caused by a vibration of the apparatus. At this time, if the apparatus main body communicates with the ID chip 35Y, a communication error occurs, wrong information is written on the ID chip 35Y, or wrong information is read out from the ID chip 35Y.